The present invention is directed to correction tapes having dye migration blocking properties. More specifically, the present invention includes a correction tape having a dye migration barrier. The dye migration barrier comprises an organic material that serves as a physical barrier to prevent ink dye from markings covered by the correction tape from migrating to an upper visible surface of the correction tape. Additionally, the present invention is directed to a process for the manufacture of a correction tape having a dye migration barrier.
Correction tape is a commonly used method to cover markings. The tape typically comprises two parts, a polymeric support member as a base and a correction medium releasably attached to the base. A correction medium may be multi-layered, and may contain pigments, fillers, such as clay, a polymeric binder and dispersant to anchor the pigments to the paper, as well as, a dispersant medium or solvent to maintain fluid viscosity. The correction medium is later transferred onto paper to cover markings once pressure is applied on the tape.
Conventional correction tapes typically allow ink dyes from the covered markings to bleed through the applied correction medium. The dissolution of the underlying ink dyes from the reaction of the ink dye with the correction medium causes the so-called bleeding or smudging of the markings into the correction medium, which discolors the correction medium on the corrected marking. Bleeding causes the typically white correction medium to assume a bluish or reddish tint or other type of blemish color due to the ink dye migrating toward the upper visible surface of the layer of correction medium. This bleeding effect is a known shortcoming of conventional correction tapes.
Correction fluids have been developed to solve the problem of bleed-through. See, European Publication No. 0 647 689 A1, PCT Publication No. WO 92/07039, PCT Publication No. WO 94/29393, PCT Publication No. WO 96/01878, and PCT Publication No. WO 98/30641.
Japanese Patent No. 2,692,642 discloses a correction tape comprising a correction material, a metal thin film layer, and an adhesive layer. The metal thin film layer provides a masking effect. The correction medium layer has the same color tone as that of a plain paper effected by incorporating a white pigment into a resin material or by providing a white printing layer on the surface of the base material layer. The correction tape manufactured with a metal thin film layer is costly because the metal thin film layer is applied using specialized vapor deposition techniques instead of standard layering techniques. Additionally, the vapor deposition of a metal requires harsh manufacturing conditions that strain the correction medium layer such as high temperatures, low pressures, and drying periods under vacuum.
Some of the commercially available correction tape products are made using polymers dissolved in organic solvents which provide some protection against bleeding, however, environmental regulations restrict the use of organic solvents on an industrial scale due to pollution problems. Measures taken to decrease the environmental impact of the use of organic solvents increase production costs of correction tapes. Other commercial products do not have adequate bleed inhibiting characteristics.
Despite these efforts correction tapes having better bleed through resistance are still desired by the industry. As new water and solvent based ink compositions are developed, new compositions and formulations of correction tapes are necessary to maintain good bleed through resistance.